TUESDAY, Jan. 29 (HealthDay News) -- There's no proof to support the widely held belief that July is the worst time of year to have spinal surgery, according to a new study.

Researchers from the Mayo Clinic in Rochester, Minn., looked at whether there was any evidence of the so-called "July Effect," which is the notion that the arrival of new residents and fellows at teaching hospitals each July makes it the worst time of year to be a patient.

The investigators examined data on nearly 1 million patients who had spinal surgery from 2001 to 2008 and found that the month in which they had surgery had little effect on their outcomes.

Incidents of all negative outcomes studied were slightly higher in teaching hospitals than in non-teaching hospitals. In the teaching hospitals, there were minimally higher rates of infection after surgery, and patient discharge to a long-term care facility in July compared with other months.

These rates were not high enough, however, to establish a "July Effect," the researchers said.

Rates of in-hospital deaths and complications after surgery did not differ according to the month that patients were admitted to hospital, according to the study, which was published online Jan. 29 in the Journal of Neurosurgery: Spine.

"We hope that our findings will reassure patients that they are not at higher risk of medical complications if they undergo spinal surgery during July as compared to other times of the year," study co-author Jennifer McDonald said in a Mayo news release. "While we only looked at spinal surgeries, we think it's likely we'd find similar outcomes among other surgeries and procedures."